Uv-photoprotective dibenzoylmethane compositions comprising photostabilizing amounts of benzalmalonate silanes

ABSTRACT

Topically applicable, stable, UV-photoprotective cosmetic/dermatological compositions well suited for the photoprotection of human skin and/or hair against the damaging effects of TV-A and UV-B irradiation, comprise (a) an effective UV-photoprotecting amount of at least one dibenzoylmethane UV-sunscreen compound and (b) an effective dibenzoylmethane compound (a) photostabilizing amount of at least one benzalmalonate silane having the structural formula (I):

CROSS-REFERENCE TO PRIORITY APPLICATION

[0001] This application claims priority under 35 U.S.C. §119 ofFR-97/02759, filed Mar. 7, 1997, hereby expressly incorporated byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field of the Invention

[0003] The present invention relates to novel topically applicableUV-photoprotective compositions containing at least one normallyphotolabile dibenzoylmethane UV-screening compound and, as aphotostabilizer therefor, an effective amount of at least one particularbenzalmalonate silane.

[0004] This invention also relates to certain novel processes for thesynthesis of said particular benzalmalonate silanes.

[0005] 2. Description of the Prior Art

[0006] It is known to this art that light radiation of wavelengthsranging from 280 nm to 400 nm promote tanning of the human epidermis,and that radiation of wavelengths more particularly ranging from 280 to320 nm, i.e., UV-B irradiation, causes erythemas and skin burns whichare detrimental to the development of natural bronzing and tanning. Forthese reasons, as well as for aesthetic reasons, there is a constantdemand for means to control this natural bronzing and thus control thecoloration of the skin; it is thus advisable to filter such UV-Bradiation from the skin.

[0007] It is also known to this art that UV-A irradiation, ofwavelengths of from 320 to 400 nm, which promotes tanning of the skin,also adversely affects it, especially in the case of a sensitive skin orof a skin which is continuously exposed to solar radiation. The UV-Arays, in particular, cause a loss in the elasticity of the skin and theappearance of wrinkles, resulting in premature cutaneous aging. UV-Aradiation promotes triggering of the erythematous reaction or amplifiesthis reaction in certain individuals and can even be the source ofphototoxic or photoallergic reactions. Thus, for aesthetic and cosmeticreasons such as the preservation of the natural elasticity of the skin,for example, more and more individuals seek to control the effect ofUV-A rays on their skin. It is thus desirable to also filter out UV-Aradiation.

[0008] In this respect, one class of UV-A filters of particular interestcomprises the dibenzoylmethane compounds, and especially4-tert-butyl-4′-methoxydibenzoylmethane, which indeed have a greatcapacity for intrinsic absorption. These dibenzoylmethane compounds,which are per se well known as active filters in the UV-A region, aredescribed, in particular, in FR-A-2,326,405 and FR-2,440,933, as well asin EP-A-0,114,607; 4-tert-butyl-4′-methoxydibenzoylmethane is alsocommercially available under the trademark “PARSOL 1789” by GIVAUDAN.

[0009] Unfortunately, the dibenzoylmethane derivatives are compoundswhich are relatively sensitive to ultraviolet radiation (especially UV-Airradiation), namely, they have an unfortunate tendency to degrade to amore or less rapid extent under the action of such radiation. Thus, thissubstantial lack of photochemical stability of dibenzoylmethanecompounds with regard to ultraviolet radiation which by their verynature they are intended to be subjected, does not permit constantprotection to be guaranteed during prolonged exposure to the sun, suchthat, in a restrictive fashion, repeated applications at regular andclose intervals of time must be carried out by the user to provide anefficacious protection of the skin against UV rays.

[0010] The photostabilization of dibenzoylmethane compounds with respectto UV radiation remains a problem which to date has not satisfactorilybeen resolved.

[0011] Thus, EP-A-0,709,080 describes combining dibenzoylmethanederivatives with very specific benzalmalonate derivatives, namely,benzalmalonate siloxanes, in order to decrease the photoinstability ofsaid dibenzoylmethane compounds. In particular, this ′080 applicationmandates that the siloxane structure of these compounds is essential toprovide satisfactory photostabilization (see page 10, line 22 ofEP-A-0,709,080). However, these benzalmalonate siloxanes are moleculeswhich are bulky and complex to synthesize.

SUMMARY OF THE INVENTION

[0012] It has now unexpectedly and surprisingly been determined thatcombining the dibenzoylmethane compounds indicated above with aphotostabilizing effective amount, not of a benzalmalonate siloxane, butof a benzalmalonate silane, markedly enhances the photochemicalstability (or photostability) of these same dibenzoylmethane compounds.

[0013] It has also been determined that certain novel processes for thepreparation of various of these benzalmalonate silanes present theadvantage of being much more easy to carry out than the hydrosilylationprocess described in the prior art, for example, in JP-07/330,779.

[0014] Thus, the present invention features improving the photostabilityof at least one photolabile dibenzoylmethane compound with respect toUV-radiation, by intimately combining said dibenzoylmethane compoundswith an effective amount of at least one benzalmalonate silane havingthe following structural formula (I):

[0015] in which R₁, R₂ and R₃, which may be identical or different, areeach an optionally halogenated C₁-C₁₀ alkyl radical or a phenyl radical;R₄ and P₅, which may be identical or different, are each a hydrogenatom, a hydroxyl radical, a C₁-C₆ alkyl radical, a C₁-C₆ alkoxy radical,or a trimethylsilyloxy radical; R₆ and R₇, which may be identical ordifferent, are each a C₁-C₈ alkyl radical; a is equal to 0 or 1; and Yis a divalent radical having one of the following formulae (1) to (4):

[0016] wherein R₈ is a hydrogen atom or a C₁-C₅ alkyl radical, and p isan integer ranging from 1 to 10, inclusive, with the proviso that thegroup -Y- (O)_(a)- and the two groups R₄ and R₅ are variously bonded tothe aromatic ring member in the para-position and in the twometa-positions with respect to the radical -CH=C-[(CO₂R₆)](CO₂R₇).

DETAILED DESCRIPTION OF BEST MODE AND SPECIFIC/PREFERRED EMBODIMENTS OFTHE INVENTION

[0017] More particularly according to the present invention, the subjectcosmetic and/or dermatological compositions present the advantage ofbeing particularly photostable, even after prolonged exposure to TV-Aand UV-B radiation. This radiation can be of natural (sun) or artificial(UV lamp) origin. In addition, as described below, the benzalmalonatesilanes being molecules which are quite easy to synthesize, thecompositions according to the invention are likewise readily formulatedindustrially.

[0018] The present invention thus features the use of a benzalmalonatesilane to enhance the stability with respect to UV rays of adibenzoylmethane compound contained in a UV-screening cosmetic and/ordermatological composition.

[0019] As indicated above, the dibenzoylmethane derivatives that arephotostabilized according to the present invention are compounds whichare per se known to this art and are described in the abovementionedFR-A-2,326,405, FR-A-2,440,933 and EP-A-0,114,607.

[0020] According to the present invention, it is of course envisioned toemploy one or more dibenzoylmethane compounds.

[0021] Particularly exemplary dibenzoylmethane compounds according tothe present invention include the following:

[0022] 2-methyldibenzoylmethane;

[0023] 4-methyldibenzoylmethane;

[0024] 4-isopropyldibenzoylmethane;

[0025] 4-tert-butyldibenzoylmethane;

[0026] 2,4-dimethyldibenzoylmethane;

[0027] 2,5-dimethyldibenzoylmethane;

[0028] 4,4-diisopropyldibenzoylmethane;

[0029] 4-tert-butyl-4′-methoxydibenzoylmethane;

[0030] 2-methyl-5-isopropyl-4′-methoxydibenzoylmethane;

[0031] 2-methyl-5-tert-butyl-4′-methoxydibenzoylmethane;

[0032] 2,4-dimethyl-4′-methoxydibenzoylmethane;

[0033] 2,6-dimethyl-4-tert-butyl-4′-methoxydibenzoylmethane;

[0034] 4,4′-dimethoxydibenzoylmethane.

[0035] Among the dibenzoylmethane compounds indicated above, preferredis 4-tert-butyl-4′-methoxydibenzoylmethane, especially that commerciallyavailable under the trademark “PARSOL 1789” by GIVAUDAN, this filterthus having the following structural formula:

[0036] Another preferred dibenzoylmethane compound according to thepresent invention is 4-isopropyldibenzoylmethane, a filter marketedunder the trademark “EUSOLEX 8020” by MERCK, and having the followingstructural formula:

[0037] The dibenzoylmethane derivatives are advantageously present inthe stabilized compositions according to the invention in amountsgenerally ranging from 0.01% to 10% by weight and preferably in amountsranging from 0.3% to 5 % by weight, with respect to the total weight ofthe composition.

[0038] As indicated above, the benzalmalonate silanes according to thisinvention are known compounds which are described, especially, inJP-07/330,779. These have the following structural formula (I):

[0039] in which R₁, R₂ and R₃, which may be identical or different, areeach an optionally halogenated C₁-C₁₀ alkyl radical or a phenyl radical;R₄ and R₅, which may be identical or different, are each a hydrogenatom, a hydroxyl radical, a C₁-C₆ alkyl radical, a C₁-C₆ alkoxy radical,or a trimethylsilyloxy radical; R₆ and R₇, which may be identical ordifferent, are each a C₁-C₈ alkyl radical; a is equal to 0 or 1; and Yis a divalent radical having one of the following formulae (1) to (4):

[0040] wherein R₈ is a hydrogen atom or a C₁-C₅ alkyl radical, and p isan integer ranging from 1 to 10, inclusive, with the proviso that thegroup -Y- (O)_(a) and the two groups R₄ and R₅, are variously bonded tothe aromatic ring member in the para-position and in the twometa-positions with respect to the radical -CH=C-[(CO₂R₆)](CO₂R₇).

[0041] The benzalmalonate silanes according to the invention, as willlater be seen, present the advantage of being much more simple tosynthesize and to purify than the benzalmalonate siloxanes known to theprior art. Too, the process of the invention is likewise easier to carryout on an industrial scale.

[0042] In a preferred embodiment of the invention, the silanes offormula (1) above and satisfying at least one, preferably all, of thefollowing conditions are employed:

[0043] R₁ is methyl,

[0044] R₂ is methyl or ethyl,

[0045] R₃ is methyl,

[0046] Y is a divalent radical of formula (3) or (4) in which R₈ ishydrogen or methyl and p is 1 or 2,

[0047] a is 1,

[0048] R₄ is hydrogen or a methoxy radical,

[0049] R₅ is hydrogen,

[0050] R₆ is methyl or ethyl,

[0051] R₇ is methyl or ethyl,

[0052] the -Y- (O)_(a) group is bonded to the aromatic ring member inthe para-position with respect to the -CH=C-[(CO₂R₆)](CO₂R₇) radical.

[0053] Particularly suitable silanes according to the present inventionare the compounds having the following structural formulae (5), (6) and(7):

[0054] To prepare the compounds of formula (I) in which a=0, ahydrosilylation reaction is carried out between the correspondingunsaturated derivative and the corresponding silane such as is describedin JP-07/330,779.

[0055] The present invention features a first process (reaction schemeA) for the preparation of the compounds of formula (I) in which a is 1,comprising, in a first step, reacting an aromatic hydroxybenzaldehyde offormula (8) below with a halogenated silane derivative of formula (9)below. Then, in a second step, the benzaldehyde of formula (10) thusobtained is condensed with a malonic diester of formula (11) below.Preferably, the aromatic hydroxybenzaldehyde and the halogenated silanederivative are reacted in the presence of a base according to aconventional alkylation reaction, the condensation of the benzaldehydeobtained with the malonic diester being carried out in toluene in thepresence of piperidinium acetate as a catalyst (Knoevenagelcondensation) according to the following reaction scheme:

[0056] in which Y, R₁, R₂, R₃, R₄, R₅, R₆ and R₇ are as defined abovefor formula (1) and Hal is a halogen, preferably chlorine.

[0057] The present invention also features a second process (reactionscheme B) for the preparation of the compounds of formula (1) in which ais 1, comprising reacting a hydroxybenzalmalonate of formula (12) belowwith a halogenated silane derivative of formula (9). Preferably, thehydroxybenzalmalonate and the halogenated silane derivative are reactedin the presence of a base according to a conventional alkylationreaction according to the following scheme:

[0058] in which Y, R₁, R₂, R₃, R₄, R₅, R₆ and R₇ are as defined informula (I) and Hal is a halogen, preferably chlorine.

[0059] The above syntheses present the advantage of being easier tocarry out than hydrosilylation reactions.

[0060] Exemplary aromatic benzaldehyde derivatives include4-hydroxybenzaldehyde or vanillin, which are commercially availableproducts.

[0061] Exemplary malonic ester derivatives include dimethyl malonate ordiethyl malonate, which are also commercially available.

[0062] An exemplary hydroxybenzalmalonate derivative is dimethylparahydroxybenzalmalonate marketed by ACROS.

[0063] And an exemplary silane halide derivative ischloropropyltrimethylsilane, marketed by WACKER.

[0064] By an “effective amount” of benzalmalonate silane according tothe invention is intended an amount sufficient to provide a notable andsignificant improvement in the photostability of the dibenzoylmethanederivative(s) contained in the composition. The minimum amount ofstabilizing agent to be employed, which can vary according to the natureof the cosmetically acceptable support (vehicle, diluent or carrier)reserved for the composition, can be determined without any difficultyby means of a conventional photostability measuring test, such asdescribed in FR-A-2,607,700.

[0065] The benzalmalonate silanes are generally present in thecompositions according to the invention in a content at least equal to0.5% by weight, with respect to the total weight of the composition.More preferably, this amount ranges from 0.5% to 20% by weight, withrespect to the total weight of the composition.

[0066] The cosmetic and/or dermatological compositions of this inventioncan, of course, contain one or more hydrophilic or lipophiliccomplementary screening agents active in the UV-A and/or UV-B(absorbers) ranges. These complementary sunscreens are advantageouslyselected from among cinnamic derivatives, the salicylic derivatives, thebenzylidene camphor derivatives, the benzimidazole derivatives, thetriazine derivatives, the benzophenone derivatives, the β,β′-diphenylacrylate derivatives, the p-aminobenzoic acid derivatives,the sunscreen polymers and filtering silicones described in WO-93/04665.Other examples of organic sunscreens are described in EP-A- 487,404.

[0067] The compositions according to the invention can also containartificial skin bronzing and/or browning agents (self-tanning agents)such as, for example, dihydroxyacetone (DHA).

[0068] The cosmetic and/or dermatological compositions of this inventioncan also contain pigments or nanopigments (average size of the primaryparticles: generally ranging from 5 nm to 100 nm, preferably from 10 and50 nm) of coated or un-coated metallic oxides such as, for example,nanopigments of titanium dioxide (amorphous or crystallized in rutileand/or anatase form), of iron, of zinc, of zirconium, or of cerium,which are all photoprotective agents per se well known and acting byphysical blocking (reflection and/or diffusion) of the UV radiation.Conventional coating agents are, in addition, alumina and/or aluminumstearate. Such nanopigments of metallic oxides, coated or un-coated, aredescribed, in particular, in EP-A-518,772 and EP-A-518,773.

[0069] The compositions of the present invention can additionallycomprise conventional cosmetic adjuvants and additives, especiallyselected from among fatty substances, organic solvents, ionic ornon-ionic thickeners, softeners, antioxidants, anti-free radical agents,opacifiers, stabilizers, emollients, silicones, x-hydroxy acids,anti-foaming agents, hydrating agents, vitamins, perfumes,preservatives, surfactants, fillers, sequestrants, polymers,propellants, insect repellents, basifying or acidifying agents,colorants, dyes, pigments, or any other ingredients usually used in thecosmetic and/or dermatological field, in particular for the formulationof sunscreen compositions as emulsions.

[0070] The fatty substances can be an oil or a wax or mixtures thereof.By “oil” is intended a compound which is liquid at ambient temperature.By “wax” is intended a solid or substantially solid compound at ambienttemperature, whose melting point is generally greater than 35° C.

[0071] Exemplary oils include mineral oils (vaseline); vegetable oils(sweet almond oil, macadamia oil, blackcurrant seed oil, jojoba oil);synthetic oils such as perhydrosqualene, alcohols, fatty acids or esters(such as benzoates of C₁₂-C₁₅ alcohols marketed under the trademark“Finsolv TN” by Finetex, octyl palmitate, isopropyl lanolate,trigylcerides including those of capric/caprylic acids), oxyethylene oroxypropylene fatty esters and ethers; silicone oils (cyclomethicone,polydimethylsiloxanes or PDMS) or fluorinated oils, polyalkylenes.

[0072] Exemplary waxy compounds include paraffin, carnauba wax, beeswax,hydrogenated castor oil.

[0073] Exemplary organic solvents include the lower alcohols andpolyols.

[0074] And exemplary thickeners are crosslinked polyacrylic acids, guargums and modified or unmodified celluloses such as hydroxypropylatedguar gum, methylhydroxyethylcellulose and hydroxypropylmethylcellulose.

[0075] It will of course be appreciated that one skilled in this artwill take care to select the possible complementary compound(s)indicated above (in particular the complementary sunscreens and/or theamounts thereof such that the advantageous properties intrinsicallyassociated with the compositions of the invention will not, or will notsubstantially be, altered by the additions envisioned.

[0076] The compositions according to the invention can be formulatedaccording to the techniques well know to this art, in particular thoseintended for the preparation of emulsions of oil-in-water orwater-in-oil type.

[0077] The subject compositions are advantageously formulated in simpleor complex emulsion form (W/O, O/W, O/W/O or W/O/W) such as a cream, amilk, or in the form of a gel or of a cream gel, a powder, a solid stickand can optionally be presented as an aerosol and be present in the formof foam or of spray.

[0078] Preferably, the compositions according to the invention areformulated as oil-in-water emulsions.

[0079] When an emulsion is concerned, the aqueous phase of this cancomprise a non-ionic vesicle dispersion prepared according to knowntechniques (Bangham, Standish and Watkins, J. Mol. Biol., 13, 238(1965), FR-2,315,991 and FR-2,416,008).

[0080] The cosmetic and/or dermatological compositions of the inventionare useful photoprotective compositions for the human epidermis or hairagainst ultraviolet radiation, as sunscreen compositions or as a makeupproduct.

[0081] When the cosmetic compositions according to the invention areused for the protection of the human epidermis against UV rays, or assunscreen compositions, they can be formulated in suspension ordispersion form in solvents or fatty substances, in non-ionic vesicledispersion form, or, alternatively, in emulsion form, preferably ofoil-in-water type, such as a cream or a milk, a lotion, gel, cream gel,ointment, solid tube, stick, aerosol mousse or spray.

[0082] When the cosmetic compositions according to the invention areused for the protection of the hair, same can be formulated as ashampoo, lotion, gel, emulsion, non-ionic vesicle dispersion, hairlacquer and can constitute, for example, a composition for rinsing, tobe applied before or after shampooing, before or after coloring orbleaching, before, during or after permanent waving or straightening, astyling or treating lotion or gel, a lotion or a gel for blowdrying orhairsetting, a permanent wave or a straightening, coloring or bleachingcomposition for the hair.

[0083] When the compositions are used as makeup products for theeyelashes, eyebrows or the skin, such as a cream for the treatment ofthe epidermis, foundation cream, lipstick, eyeshadow, blusher, mascaraor eyeliner, same may be formulated in anhydrous or aqueous, solid orpasty form, such as oil-in-water or water-in-oil emulsions, non-ionicvesicle dispersions, or, alternatively, suspensions.

[0084] The sunscreen formulations in accordance with the invention areadvantageously formulated with a support of oil-in-water emulsion type,the aqueous phase (especially comprising the hydrophilic sunscreens)generally constitutes from 50% to 95% by weight, preferably from 70% to90% by weight, with respect to the total weight of the formulation, theoily phase (especially comprising the lipophilic sunscreens) from 5% to50% by weight, preferably from 10% to 30% by weight, with respect to thetotal weight of the formulation, and the (co)emulsifier(s) from 0.5% to20% by weight, preferably from 2% to 10% by weight, with respect to thetotal weight of the formulation.

[0085] In order to further illustrate the present invention and theadvantages thereof, the following specific examples are given, it beingunderstood that same are intended only as illustrative and in nowiselimitative.

EXAMPLE 1

[0086]

[0087] (a) First Step

[0088] Preparation of3-methoxy-4(3-trimethyl-silanylpropyloxy)benzaldehyde

[0089] 3-Chloropropyltrimethylsilane (33.14 g, 0.22 mol) was addeddropwise over the course of 20 minutes into a mixture of vanillin (30.4g, 0.2 mol) and potassium carbonate (30.4 g, 0.22 mol) in 150 ml of drydimethylformamide (DMF) heated to 50° C. under nitrogen. The mixture wasmaintained for 4 hours at 95°-110° C. The reaction mixture was cooledand poured into ice water. The aqueous phase was extracted 3 times withdichloromethane. The organic phases were dried over sodium sulfate andconcentrated in vacuo. After distillation in vacuo (0.04 mm Hg), 47.5 g(yield: 89%) of 3-methoxy4-(3-trimethylsilanylpropyloxy)benzaldehydewere obtained in the form of a slightly pink oil distilling at 112°-114° C. and employed as such in the following step (b).

(b) Second Step

[0090] Preparation of dimethyl2-[3-methoxy-4-(3-trimethylsilanylpropyloxy)benzylidene]malonate:

[0091] A mixture of the compound prepared in step (a) (13.3 g, 0.05 mol)and of dimethyl malonate (7.93 g, 0.06 mol) in 20 ml of toluene washeated to reflux for 3 hours in the presence of 0.5 ml of piperidine and0.3 ml of acetic acid. The reaction mixture was cooled and poured intowater and then extracted with diisopropyl ether. The organic phase wasdried over sodium sulfate and concentrated. After crystallization in a90:10 by volume methanol/water mixture, 15 g (yield: 79%) of thecompound having the following characteristics were obtained: (i) whitepowder (ii) m.p.: 51°-52° C. (iii) UV (Ethanol) λ_(max) = 331 nm,ε_(max) = 20,300

[0092] Elemental analysis for C₁₉H₂₈O₆Si theory: C: 59.97 H: 7.42 Si:7.38 found: C: 59.80 H: 9.35 Si: 7.30

EXAMPLE 2

[0093]

[0094] 3-Chloropropyltrimethylsilane (16.57 g, 0.11 mol) was addeddropwise over the course of 10 minutes into a mixture of diethyl4-hydroxybenzalmalonate (15.18 g, 0.11 mol) and potassium carbonate(15.18 g, 0.11 mol) in 100 ml of dry DMF heated to 80° C. undernitrogen. The mixture was maintained for 3 hours, 30 minutes, at120°-130° C. The reaction mixture was then cooled and poured into icewater. The aqueous phase was extracted 2 times with dichloromethane. Theorganic phases were washed with water and then dried over sodium sulfateand concentrated in vacuo. After crystallization in methanol, 31.6 g(yield: 76%) of the compound having the following characteristics wereobtained: (i) white powder (ii) m.p.: 34°-35° C. (iii) UV (Ethanol)λ_(max) = 314 nm, ε_(max) = 26,400

[0095] Elemental analysis for C₂₀H₃₀O₅Si theory C: 63.46 H: 7.99 Si:7.42 found C: 63.31 H: 7.90 Si: 7.50

[0096] Thus, it has been determined that the benzalmalonate silaneobtained above stabilized 4tert-butyl-4′-methoxydibenzoylmethane withrespect to ultraviolet radiation in such manner that was at least asefficacious as the benzalmalonate siloxanes described in EP-A-0,709,080.

[0097] While the invention has been described in terms of variouspreferred embodiments, the skilled artisan will appreciate that variousmodifications, substitutions, omissions, and changes may be made withoutdeparting from the spirit thereof. Accordingly, it is intended that thescope of the present invention be limited solely by the scope of thefollowing claims, including equivalents thereof.

What is claimed is:
 1. A topically applicable sunscreen/cosmeticcomposition suited for the UV-photoprotection of human skin and/or hair,comprising (a) an effective UV-photoprotecting amount of at least onedibenzoylmethane UV-sunscreen compound and (b) an effectivedibenzoylmethane compound (a) photostabilizing amount of at least onebenzalmalonate silane having the structural formula (I):

in which R₁, R₂ and R₃, which may be identical or different, are each anoptionally halogenated C₁-C₁₀ alkyl radical or a phenyl radical; R₄ andR₅, which may be identical or different, are each a hydrogen atom, ahydroxyl group, a C₁-C₆ alkyl radical, a C₁-C₆ alkoxy radical, or atrimethylsilyloxy radical; R₆ and R₇, which may be identical ordifferent, are each a C₁-C₈ alkyl radical; a is equal to 0 or 1; and Yis a divalent radical having one of the following formulae (1) to (4):

wherein R₁ is a hydrogen atom or a C₁-C₅ alkyl radical, and p is aninteger ranging from 1 to 10, inclusive, with the proviso that the group-Y- (O)_(a)- and the two radicals R₄ and R₅ are variously bonded to thearomatic ring member in the para-position and in the two meta-positionswith respect to the radical -CH=C-[(CO₂R₆)](CO₂R₇).
 2. Thesunscreen/cosmetic composition as defined by claim 1, formulated with atopically applicable, cosmetically/dermatologically acceptable vehicle,diluent or carrier therefor.
 3. The sunscreen/cosmetic composition asdefined by claim 1, wherein formula (I) at least one of the followingconditions is satisfied: R₁ is methyl; R₂ is methyl or ethyl; R₃ ismethyl; Y is a divalent radical of formula (3) or (4) in which R₈ ishydrogen or methyl and p is 1 or 2; a is 1; R₄ is hydrogen or a methoxyradical; R₅ is hydrogen; R₆ is methyl or ethyl; R₇ is methyl or ethyl;and/or the -Y- (O)_(a)- group is bonded to the aromatic ring member inthe para-position with respect to the -CH=C-[(CO₂R₆)](CO₂R₇) radical. 4.The sunscreen/cosmetic composition as defined by claim 1, said at leastone benzalmalonate silane (I) having one of the following formulae (5),(6) or (7):


5. The sunscreen/cosmetic composition as defined by claim 1, said atleast one dibenzoylmethane compound comprising 2-methyldibenzoylmethane,4-methyldibenzoylmethane, 4-isopropyldibenzoylmethane,4-tert-butyldibenzoylmethane, 2,4-dimethyldibenzoylmethane,2,5-dimethyldibenzoylmethane, 4,4′-diisopropyldibenzoylmethane,4-tert-butyl-4′-methoxydibenzoylmethane,2-methyl-5-isopropyl-4′-methoxydibenzoylmethane,2-methyl-5-tert-butyl-4′-methoxydibenzoylmethane,2,4-dimethyl-4′-methoxydibenzoylmethane,2,6-dimethyl-4tert-butyl-4′-methoxy-dibenzoylmethane, and/or4,4′-dimethoxydibenzoylmethane.
 6. The sunscreen/cosmetic composition asdefined by claim 5, said at least one dibenzoylmethane compoundcomprising 4-tert-butyl-4′-methoxydibenzoylmethane.
 7. Thesunscreen/cosmetic composition as defined by claim 5, said at least onedibenzoylmethane compound comprising 4-isopropyldibenzoylmethane.
 8. Thesunscreen/cosmetic composition as defined by claim 1, comprising from0.5% to 20% by weight of said at least one benzalmalonate silane (I). 9.The sunscreen/cosmetic composition as defined by claim 1, furthercomprising at least one additional hydrophilic or lipophilic organicUV-A and/or UV-B sunscreen.
 10. The sunscreen/cosmetic composition asdefined by claim 1, further comprising at least one active agent for theartificial tanning and/or browning of human skin.
 11. Thesunscreen/cosmetic composition as defined by claim 1, further comprisingat least one additive or adjuvant which comprises a fat, organicsolvent, ionic or nonionic thickening agent, softener, antioxidant,anti-free radical antioxidant, opacifying agent, stabilizing agent,emollient, silicone, x-hydroxy acid, anti-foaming agent, hydratingagent, vitamin, fragrance, preservative, surfactant, filler,sequestering agent, polymer, propellant, insect repellent, basifying oracidifying agent, dye, colorant, pigment, nanopigment, or mixturethereof.
 12. The sunscreen/cosmetic composition as defined by claim 1,comprising a nonionic vesicle dispersion, emulsion, cream, milk, gel,cream gel, ointment, suspension, dispersion, powder, solid, stick, foamor spray.
 13. The sunscreen/cosmetic composition as defined by claim 1,comprising a makeup.
 14. The sunscreen/cosmetic composition as definedby claim 1, comprising an anhydrous or aqueous solid or paste, emulsion,suspension, or dispersion.
 15. The sunscreen/cosmetic composition asdefined by claim 1, comprising a shampoo, lotion, gel, emulsion,nonionic vesicle dispersion, hair lacquer, or rinse.
 16. Thesunscreen/cosmetic composition as defined by claim 1, comprising a skincream, foundation, face powder, lipstick, mascara, eyeliner, hair gel,hair lotion, or shampoo.
 17. A method for protecting human skin and/orhair against the deleterious effects of ultraviolet irradiation,comprising topically applying thereto an effective amount of thesunscreen/cosmetic composition as defined by claim
 1. 18. A method forprotecting human skin and/or hair against the deleterious effects ofsolar radiation, comprising topically applying thereto an effectiveamount of the sunscreen/cosmetic composition as defined by claim
 1. 19.A process for the preparation of a benzalmalonate silane (I) as definedin claim 1 and wherein a is 1, comprising reacting an aromatichydroxybenzaldehyde having the structural formula (8):

with a halogenated silane having the formula (9): Hal-Y-SiR₁R₂R₃ (9) inwhich Hal is a halogen atom, and then condensing the benzaldehyde thusobtained with a malonic diester having the structural formula (11):


20. The process as defined by claim 19, carried out according to thefollowing reaction mechanism:


21. A process for the preparation of a benzalmalonate silane (I) asdefined in claim 1 and wherein a is 1, comprising reacting ahydroxybenzalmalonate having the structural formula (12):

with a halogenated silane having the formula (9): Hal-Y-SiR₁R₂R₃ (9) inwhich Hal is a halogen atom.
 22. The process as defined by claim 21,carried out according to the following reaction mechanism: